Method and a device for mixing and homogenizing of bulk material

ABSTRACT

In a method and means for mixing and homogenizing bulk material such as lump ore and ore concentrates, in which a mixing heap is formed by dumping the material as a large number of layers one on top of the other, said mixing heap thereupon being dug off over the entire height, in which for forming said mixing heap the material to be dumped in layers is fed by a digging machine onto a belt conveyor system and is dumped from this system by a longitudinally moving dumping machine onto the said mixing heap, the material during transport to the dumping machine passes through a throughflow hopper, from which it is discharged in a constant flow, and the speed of the digging machine is controlled in dependency upon the filling of this hopper by special mechanisms, preferably comprising a metering device below the hopper, weight signalling means, weight-to-volume converting means, and special supports and controls.

United States Patent [191 Burger et al.

1 Jan. 1,1974

[ METHOD AND A DEVICE FOR MIXING AND HOMOGENIZING OF BULK MATERIAL [75]Inventors: ,lacobus .1. Burger, Driehuis; Gerrit De Jong, Velsen; GradusJ. J. Den Boer, Driehuis, all of Netherlands 22 Filed: Sept. 10, 1971 21Appl. No.: 179,499

[30] Foreign Application Priority Data Sept. 10, 1970 Netherlands7013571 [52] US. Cl 198/36, 198/39, 198/44, 214/2, 214/10, 214/17 CA,214/152 [51] Int. Cl. B65g 57/02 [58] Field of Search 214/10, 17 CA,152, 214/2; 198/36, 39

[56] References Cited UNITED STATES PATENTS 3,606,954 9/1971 Mayer214/10 2,737,997 3/1956 Himmelherer et al. 214/17 CA X 3,165,195 1/1965Sass et a1. 198/39 X 3,358,855 12/1967 Carlton et a1 214/10 3,470,63510/1969 Langner et a1.... 198/36 X 3,682,339 8/1972 Knappstein 222/58 XFOREIGN PATENTS OR APPLICATIONS 1,150,604 4/1969 Great Britain 214/10Primary Examiner-Gera1d M. Forlenza Assistant Examiner-Frank E. WernerAttorney-.1. Y. Houghton [5 7] ABSTRACT In a method and means for mixingand homogenizing bulk material such as lump ore and ore concentrates, inwhich a mixing heap is formed by dumping the material as a large numberof layers one on top of the other, said mixing heap thereupon being dugoff over the entire height, in which for forming said mixing heap thematerial to be dumped in layers is fed by a digging machine onto a beltconveyor system and is dumped from this system by a longitudinallymoving dumping machine onto the said mixing heap, the material duringtransport to the dumping machine passes through a throughflow hopper,from which it is discharged in a constant flow, and the speed of thedigging machine is controlled in dependency upon the filling of thishopper by special mechanisms, preferably comprising a metering devicebelow the hopper, weight signalling means, weight-to-volume convertingmeans, and special supports and controls.

6 Claims, 3 Drawing Figures PATENTEU H974 3.782.528

sum 2 or 2 INVENTORi .Jk 5U; BURGER Gmw/r 5 6mm U, /.Jf Dad/B 4.

ATTORNEY METHOD AND A DEVICE FOR MIXING AND I-IOMOGENIZING OF BULKMATERIAL This invention relates to a method and a device for mixing andhomogenizing bulk material such as lump ore and ore concentrates, inwhich a mixing heap is formed by dumping said material as a large numberof layers one on top of the other, said mixing heap thereupon being dugoff over its entire height, in which for forming said mixing heap thematerial to be dumped in layers is fed by a digging machine onto a beltconveyor system and is dumped from this system by a longitudinallymoving dumping machine onto the said mixing heap.

When operating modern blast furnaces of high capacity it has appearedthat the course of the process in the blast furnace and the quantity andquality of the product from the blast furnace can be influencedconsiderably in a favourable direction by a very selective choice of thecharge of the blast furnace. Among other things it is in this respect ofimportance that the chemical composition of the ore supplied over anextended period is as uniform as possible. However, it has moreoverappeared that an optimum charging in many cases is only possible bymixing ores derived from different deposits.

, In order to be able to charge a blast furnace during an extendedperiod with a flow of ore which is mixed from a number of components andwhich moreover is very homogeneous in composition it has previously beenproposed to use so-called mixing beds or fields, in which a mixing heapis composed in a manner as given above and thereupon is dug off. Suchmixing heaps may have a length of e.g. 300 m and a width of e.g. m.

It is usual to build up such a mixing heap from several hundreds oflayers with the aid of a dumping machine which moves at a speed ofseveral tenths of meters per minute along the mixing heap.

Although this known method produces a very much better homogeneity ofthe ore mass, the invention aims at further improving said homogeneity.

In this respect it has appeared that notwithstanding the very largequantity of layers from which the mixing heap is composed, measurableand more than negligible differences in composition occur in productderived from said mixing heap, which cause differences, deviations andinstability in the blast furnace process. Such effects can be decreasedfurther by trying to give all the dumped layers a thickness which is asuniform as possible. In this case, however, there are considerabledifficulties because it is difficult to achieve an ore flow to themixing heap which is accurately constant.

According to the invention a solution of the problem was found in thatthe material during transport to the dumping machine passes through athroughflow hopper, from which it is discharged in a constant flow, andin that the speed of the digging machine is controlled in dependencyupon degree of filling of this hopper.

The present invention not only relates to this method, but also to adevice for the forming of uniformly built up mixing heaps of e.g. layersof several different ores, comprising a digging machine, a dumpingmachine which is longitudinally displaceablc, and a belt conveyor systemto convey material from the digging machine to the dumping machine, saiddevice being characterized in that the belt conveyor system includes athroughflow hopper for the throughflow of the material, below which ametering device is positioned, and that means are present to detect thedegree of filling of the hopper so that the speed of the digging machinecan be controlled in dependence thereon. The digging machine may beautomatically controlled in dependence on the degree of filling.

It is remarked, that, although the invention is and will be describedwith reference to the application thereof for mixing ore, comparableapplications are possible for homogenizing and mixing several otherkinds of bulk material such as sand, coals etc.

When building up a mixing heap from e.g. 400 layers it might be expectedthat variations in thickness within each of said layers will only veryslightly influence the average composition of the mixing heap asmeasured over the height thereof. Thus it is not very obvious to ascribedisturbances and differences in uniformity in the process in the blastfurnace to variations in the thickness of each individual dumped layerin the mixing heap.

it has, however, surprizingly appeared that when applying the inventionthe process in the blast furnace can be improved considerably in that itis a result of the invention that each formed layer has a more constantthickness.

The throughflow hopper serves as a buffer between the variable supply ofthe ore and the constant dis charge thereof. With the aid of a signalindicating the amount of filling of that hopper it is possible tocontrol the speed of the digging machine both by hand and automatically.In the first case the measured signal should be transferred to thedigging machine operator, who therefrom derives an indication about howto adapt the speed of his digging machine. The required signal may beobtained by photo-optical means. Also means are known to measure theamount of filling of a hopper with the aid of gamma-ray devices andsimilar means. It has appeared that such methods are difficult to applyin the prevailing circumstances and that they moreover do not give avery reliable signal. Thus it is preferred that the throughflow hopperis supported by weighing means giving an electric weighing signal, thatmoreover means are present for translating the weighing signal into avolume signal in dependency on the measured specific bulk weight of thematerial, and that this corrected signal is fed to the digging machinefor controlling the speed thereof. The measuring of the amount offilling of the hopper has thus become independent of the shape of thecone of the material which is caused by the dumping thereof into thehopper and moreover this measurement is independent of the flow of orewhich continuously falls on top of said cone. The correction for thespecific bulk weight of the material is necessary as for different typesof ore the specific gravity may vary from 1.8 to 3.2 tons per m. It ispossible to apply such a correction in such a way that each time whendigging off another type of ore the specific bulk weight is determinedand the electric weighing signal measured at the hopper is correctedwith the aid of said measured bulk weight. it is also possible todetermine the bulk weight continuously or intermittently in an automaticmanner and to have the result thereof correct the measurement of theamount of filling of the hopper.

The dimensions of the throughflow hopper are subject to conflictingrequirements. 0n the one hand this hopper should be as low as possiblein order to limit the dimensions and total cost of the conveyor systemwith inclined conveyor belts, as said belts are limited to a maximumangle of inclination.

On the other hand the maximum amount of ore which should be stored isvery large as a result of the long time of passage of the ore throughthe conveyor system from the digging machine to the hopper. Hg. with atotal throughflow time of 8 minutes and a metering capacity of thedigging machine of 2,000 tons per hour the hopper will have to be ableto buffer up to about 150 m of ore. However, if the hopper is made verylow and thus will have to have considerable horizontal dimensions thedanger exists that it will be filled asymmetrically to a large extentand thus will discharge non-uniformly and not smoothly to the meteringdevice. The solution of filling the hopper uniformly with the aid of amovable intermediary conveyor belt above the point of discharge into thehopper is not suitable as it is complicated and expensive.

In order to meet with these objections an embodiment of the invention ispreferred in which the throughflow hopper has two discharge orifices,each connected to a metering apparatus of the metering device, saidmetering apparatuses being both connected to a single conveyor belt, inwhich moreover the throughflow hopper is supported in three supports,one being a universal joint or pivot, e.g. with spherical faces to allowpivoting in all vertical directions, the other two supports beingprovided with load measuring devices and in which a control device ispresent to control the relation of the discharge speeds of the twometering apparatuses in dependence on the ratio of the signalstransmitted by the load measuring devices.

As the discharge from the hopper is distributed over two orifices, it ispossible to make the hopper considerably lower and wider. If the fillingof the hopper has a tendency to build up eccentrically, this isautomatically corrected because at the highest side of the ore heap inthe hopper the metering apparatus below it will discharge a largerquantity per unit time and the other metering apparatus will dischargeless ore. It will be clear that, in order to obtain this, it ispreferred that the two systems, each comprising a discharge opening ofthe hopper and a load measuring device, are symmetrical with respect toeach other and that the universal pivot is positioned in the plane ofsymmetry of these two systerns. Thus it is possible for the two loadmeasuring devices to transmit signals which are immediately comparableand which are able to act upon the metering apparatus related theretowithout intricate measures to give the desired results.

Apart from the fact that the two metering apparatuses should becontrollable so that the ratio of their discharge quantities per unittime can be controlled in dependence upon the filling pattern in thehopper, it is also desired that the total discharge capacity of thesemetering apparatus may be varied. In particular it is desired that inthe conveyor belt system between the throughflow hopper and the dumpingmachine there is a conveyor belt weighing apparatus, coupled through anadjustable quantity control device to the drive of the metering device,so that the total quantity metered per unit time may be controlled to bemaintained at an adjustable level. It will be clear that the signal ofthe conveyor belt weighing apparatus should be corrected for themeasured specific bulk weight of the passing ore.

Several types of metering apparatus are known for discharging materialfrom hoppers, such as screw conveyors, cell wheels and vibrating orpulsating troughs. It has appeared that the best results may be obtainedif use is made of mechanically driven pulsating troughs. In this casethere is no danger of clogging, jamming or fouling of the drivingmechanism. As compared with electromagnetically driven pulsating troughsmechanically driven troughs moreover have the advantage that they arenot or only very little dependent upon the specific bulk weight of theore. When applying an electromagnetic drive of the pulsating troughs itwould on the contrary be necessary to correct the thickness of the layerof the ore in the trough depending upon the specific bulk weight of thematerial.

In normal operation of the device described above the control systemwill be able to adapt the digging speed of the digging machine to thecapacity of the dumping machine in such a way that the pouring cone ofthe bulk material is positioned substantially halfway up the height ofthe hopper. As a result of particular conditions or circumstances at thedigging machine and/or the dumping machine situations are neverthelesspossible in which the hopper would run the risk of becoming entirelyfilled or entirely emptied. In the first case this would of course meanthat a quantity of ore would fall outside the hopper and in the lastcase the metering apparatus would be unprotected against idling andagainst damage by ore falling immediately thereon from a large height.

Thus an embodiment of the device according to the invention is preferredin which the means for controlling the speed of the digging machine arealso adapted to stop the conveyor belts for the supply to or thedischarge from the throughflow hopper when the filling amount of thehopper is higher than an upper critical level or is lower than a lowercritical level respectively.

When starting the plant or after the amount of filling of the hopper hasreached a lower critical level, the belt extending to the head of thedumping machine will no more carry over its entire length a constantweight of ore. Now if the plant will start operating the dumping machinewould during a certain time period dump a layer of unequal thicknessonto the mixing heap during movement of said machine, which is of courseundesirable. It has appeared that it is possible to avoid this objectionif according to the invention at a short distance before the dumpingmachine a conveyor belt weighing device is provided, coupled to thedriving system for this dumping machine.

The invention will now be explained with reference to the encloseddrawings giving by way of example a possible embodiment of the deviceaccording to the invention.

FIG. 1 gives somewhat diagrammatically a front view and a verticalsection through part of the device.

FIG. 2 shows a view from above of the device according to FIG. 1.

FIG. 3 gives a flow sheet and block diagram of the several controlcircuits of this device.

In FIGS. 1 and 2 reference numeral 1 shows a throughflow hopper havingtwo discharge orifices 2 and 3. The hopper is provided with three pointsof support 4, 5 and 10, in the positions indicated about the peripheryof the hopper. The supports 4 and S are supported by the supports 6 and7 of the stationary surrounding supporting structure through two loadmeasuring devices 8 and 9 adapted to give electric signals which areproportional to the load which is transmitted by said measuring devices.Such load measuring devices are generally known and thus need not be described in detail. The third support is embodied as a universal pivotingsupport, e.g. as a ball pivot.

The hopper is filled from above by a conveyor belt 1 1 with materialwhich is conveyed from a wheel digging machine not shown by anintermediary conveyor belt 12. The material flowing from the dischargeorifices 2 and 3 is fed by a conveyor belt system 13, 14 to a dumpingmachine (not shown), which strews out this material into a mixing heap.Such wheel digging machines and dumping machines are generally known andusual in the art and thus they need not be described in detail here.Between the discharge orifices 2 and 3 of the hopper and the belt 13 twometering apparatuses l5 and 116 are positioned embodied as pulsatingtroughs. Said pulsating troughs are driven by the electric motors 17 and19 energized through energy control devices 18 and 20 respectively.

The weight of the ore quantity discharged by the belt 13 is continuouslymeasured by a belt weighing device 21 pushed into contact with this belt13 at the lower surface of its operative run. Such belt weighing devicesare generally known and need not be described in detail. They give anelectric signal which is proportional to the weight of the passing load.

In FIG. 3 the control system necessary for exerting the severalfunctions of the device has been shown diagrammatically. The electricmeasuring signals of the load measuring devices 8 and 9 are suppliedthrough leads or conductors 29,30, 31 and 32 to the control device 22and to the adding device 26 respectively. The control device 22 gives asignal 34 which serves to influence the distribution of the material inthe hopper finally in such a way that the entering signals 29 and 30become equal. To this effect the signal 34 is supplied to the controldevice 23, which gives two signals, 35 and 36, one to each energy supplycontrol device 18 and 20 for the motors l7 and 19.

Also into the control device23 a signal 38 is fed, which is derived froma quantity control device 24. This control device 24 controls towards aconstant weight on belt 13 through the signal 37, derived from beltweighing device 21. Therewith this constant weight may be adjusted bymeans of an adjusting knob 25 through the adjusting signal 39 to anydesired load on the belt. The output signal 38 will control the sum ofthe signals 35 and 36.

In adding unit 26 the signals 31 and 32 of the load measuring devicesare added and are fed as an added signal 33 to the cabin of the operatorof the wheel digging machine. In said cabin the signal 33 is translatedinto an indication on the level indicator 27. As in fact the signalsgiven by the load measuring devices 8 and 9 are representative for theweight of the filling in the hopper and not for the height of fillingthereof, there is a correction knob 28 for making a correction in theindication of that level indicator 27 for the measured specific bulkweight of the ore mass in the hopper.

In FIG. 3 a situation has been drawn in which this correction is made byhand, and in which the operator of the wheel digging machine on thebasis of the visual indication of the level indicator 27 controls thespeed of digging by hand. Of course refinements are possible in which ameasuring of the specific bulk weight makes a correction in the levelindicator 27 continuously or intermittently in an automatic manner,and/or in which the apparatus 27 is used to cause an automaticcorrection of the speed ofdigging. i

The corrected signal of apparatus 27 is moreover used for making thefollowing operations when the filling in the hopper passes the criticallevels 40, 41, 42 and 43. If the amount of filling of the hopper is solow that the level of the ore drops to reach the level 43, the meteringapparatus 15 and 16 are stoppedby signal stop discharge" in order toprotect them against idling and against the action of the ore fallingfrom a considerable height onto them with empty hopper.

Only if the level in the hopper rises to reach the level 42, dischargeon", the metering apparatus are started. Thus it is avoided that themetering apparatus after having been started will have to be stoppedimmediately again by having the level in the hopper decrease again tolevel 43, stop discharge.

If for some reason the metering apparatus will stop by some disturbanceor damage, or for some other reason, the wheel digging machine 44 willautomatically be stopped. Therewith it is obtained that a considerablepart of the ore which is still present on the conveyor belts between thedigging machine and the hopper, can still be taken up by the hopper.

If the level in the hopper passes the level 41 upwardly, which is thelevel supply stop, the wheel digging machine 44 is automaticallystopped. During a time period of eg about 8 minutes the differencebetween the supplied ore and the discharged ore can be taken up in thehopper. If the level in the hopper goes down so as to pass level 41again (supply on), the wheel digging machine will begin to operateagain.

If e.g. one of the components of the system will not operate correctlyand thereby the level 40 over maximum is surpassed, a separate detectorto stop the supply belts 11 and 12 is operated.

The conveyor belt weighing device 46, which is mounted at a shortdistance before the dumping machine 45, is coupled to the drive of thisdumping machine 45. Only if this weighing device 46 measures at least acertain minimum by weight, a command is given which makes the dumpingmachine move. In a typical embodiment of the device described the hopper1 has a volume of I40 m and the metering apparatuses together have acapacity of 2,000 tons per hour.

What we claim is:

1. A method for forming a mixing heap of bulk material consisting of alarge number of horizontal layers of material, one on top of the other,comprising digging and feeding the bulk material from a material sourceto a hopper zone, maintaining a weight control of said hopper,discharging the bulk material from said hopper zone to a conveying zone,maintaining a weight control of the material discharged from said hopperzone to said conveying zone, passing the material in a constant flowfrom the conveying zone to the material heap being formed to form ahorizontal layer thereon, and correlating the control of the weight ofthe feed of the material to said hopper zone, the control of the weightof the feed of the material from the hopper zone, and the control of theweight from the zone to the heap such that the speed at which thematerial is dug is dependent upon the filling of the hopper zone.

2. A device for forming homogeneously built-up mixing heaps of bulkmaterial consisting of a plurality of horizontal layers of differentmaterials comprising a digging machine for digging the material from asupply source, longitudinally movable flow-through hopper means,conveyor means for carrying said material from said digging machine tosaid hopper means, metering means associated with the discharge end ofsaid hopper means, discharge conveyor means operatively associated withsaid metering means to receive the material from said hopper means andto discharge same to a heap to form a horizontal layer of bulk materialthereon, and means to detect the degree of filling of the hopper meansand to thereby control the speed of the digging machine.

3. A device in accordance with claim 2, characterized in that saidhopper means is provided with two discharge orifices, each of saidorifices being provided with metering means for discharging material toa single discharge conveyor means, and further characterized in thatsaid hopper means is supported by three support means, one of saidsupport means being centrally positioned to permit pivotal movement andthe other of said support means includes load measuring means therewithand a control device for controlling the relation of the discharge speedof said metering means, said load measuring means including means totransmit electrical signals indicating load measurement on each of saidsupport means to said control device to actuate same.

4. A device in accordance with claim 2, characterized in that saiddischarge conveyor means is provided with conveyor belt weighing means,and adjustable quantity control means operatively connected on one sideto said belt weighing means and on the other side to said metering meanswhereby the total quantity of material metered per unit time may becontrolled so as to be maintained at an adjustable level.

5. A device in accordance with claim 2, characterized in that themetering means are mechanically driven pulsating troughs.

6. A device in accordance with claim 2, characterized in that the meansfor controlling the speed of the digging machine will also stop theconveyor means for the supply to and discharge from said throughflowhopper means if the material in said hopper means is higher than acritical level or is lower than a critical level respectively.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT NO.

DATED Jan. 1, 1971 INVENTOR(S) Jecobus J. Burger et a1 It is certifiedthat error appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

for "Sept-either- 1 3, 1.??0 read September 1.2+, 1976-- Signed andsealed this 17th day of Jurre 1975.

(SEAL) Attest:

C. MARSHALL DANN RUTH C. MASON Commissioner of Patents and TrademarksAttesting Officer

1. A method for forming a mixing heap of bulk material consisting of alarge number of horizontal layers of material, one on top of the other,comprising digging and feeding the bulk material from a material sourceto a hopper zone, maintaining a weight control of said hopper,discharging the bulk material from said hopper zone to a conveying zone,maintaining a weight control of the material discharged from said hopperzone to said conveying zone, passing the material in a constant flowfrom the conveying zone to the material heap being formed to form ahorizontal layer thereon, and correlating the control of the weight ofthe feed of the material to said hopper zone, the control of the weightof the feed of the material from the hopper zone, and the control of theweight from the zone to the heap such that the speed at which thematerial is dug is dependent upon the filling of the hopper zone.
 2. Adevice for forming homogeneously built-up mixing heaps of bulk materialconsisting of a plurality of horizontal layers of different materialscomprising a digging machine for digging the material from a supplysource, longitudinally movable flow-through hopper means, conveyor meansfor carrying said material from said digging machine to said hoppermeans, metering means associated with the discharge end of said hoppermeans, discharge conveyor means operatively associated with saidmetering means to receive the material from said hopper means and todischarge same to a heap to form a horizontal layer of bulk materialthereon, and means to detect the degree of filling of the hopper meansand to thereby control the speed of the digging machine.
 3. A device inaccordance with claim 2, characterized in that said hopper means isprovided with two discharge orifices, each of said orifices beingprovided with metering means for discharging material to a singledischarge conveyor means, and further characterized in that said hoppermeans is supported by three support means, one of said support meansbeing centrally positioned to permit pivotal movement and the other ofsaid support means includes load measuring means therewith and a controldevice for controlling the relation of the discharge speed of saidmetering means, said load measuring means including means to transmitelectrical signals indicating load measurement on each of said supportmeans to said control device to actuaTe same.
 4. A device in accordancewith claim 2, characterized in that said discharge conveyor means isprovided with conveyor belt weighing means, and adjustable quantitycontrol means operatively connected on one side to said belt weighingmeans and on the other side to said metering means whereby the totalquantity of material metered per unit time may be controlled so as to bemaintained at an adjustable level.
 5. A device in accordance with claim2, characterized in that the metering means are mechanically drivenpulsating troughs.
 6. A device in accordance with claim 2, characterizedin that the means for controlling the speed of the digging machine willalso stop the conveyor means for the supply to and discharge from saidthroughflow hopper means if the material in said hopper means is higherthan a critical level or is lower than a critical level respectively.